There are few concrete statistics on the level of hate crime against the 1.2m people in Britain with a learning disability. In a survey by the charity Mencap, nine out of 10 said they had been bullied in the past year. Two-thirds of those questioned said they were bullied on a regular basis, and a third told of being bullied daily or weekly.

Official attempts to gather data about such crimes against disabled people generally only started last year. Experts and campaigners regard this as the most stark evidence of the failure by the authorities, and in particular the police, to take seriously the routine suffering of those with learning disabilities.

A few high profile cases, such as that of Steven Hoskin, have been widely reported. The 39-year-old, who had severe learning difficulties, was tortured and drugged before being forced over the edge of a viaduct. After two of his tormenters were convicted of murder and one of manslaughter, a serious case review revealed that police, social workers and other agencies had missed dozens of chances to intervene.

It tends to take a death to gain any serious attention, says David Congdon, the head of campaigns and policy at Mencap. What he calls "low-level harassment and bullying" goes largely unnoticed unless it drives someone to such depths of despair as it did Fiona Pilkington.

"Often people with learning disabilities aren't believed, which is a major, major problem," he said. "And they can be frightened to report incidents because they fear it will make it worse."

Victims have told the charity of offhand and dismissive reactions from police, and am impression that crimes are less serious if they are committed against a disabled person.

Ruth Scott, of the charity Scope, said: "Disabled people still find they report something to the police and nothing gets done, or the paper gets lost.

"But incidents can start at a low level and get much worse if they are not checked."

Where police fail to take action it is often because they lack the training to recognise learning disabilities and understand the impact of bullying.

Disability hate crime was recognised by law in 2005, but Leicestershire police's policy on hate crime did not even mention disability as a possible spur for abuse until it was rewritten in the wake of the Pilkington case.

Because the family's vulnerability was not recognised the endless attacks were not linked.

"That sort of failure of recording is quite widespread," Congdon said. "We only see the tip of the iceberg and that's very serious."

A similar lack of awareness pervades public opinion, according to Scope. It likens the situation to the general ignorance of race hate crime before Stephen Lawrence's death.

Last year 1,412 incidents classed as having a disability aspect were successfully prosecuted, compared with 6,689 racial incidents.

Since April last year police have been required to collect and report instances of disability hate crime in a standardised way. Congdon said awareness of the issue was growing among senior officers but it would take time to filter down to frontline police.

He would like to say the Pilkington case will be a turning point – just as Lawrence and the subsequent Macpherson report were a watershed in the treatment of race hate crime – but fears there is still some way to go.

"I hope it's a step on the way to a turning point. There's a very painful message for the police here, but the other agencies have got to ask themselves a lot of questions as well.